The present invention relates to a back-up roll which suppresses the bending of a working roll of a rolling mill during rolling.
Bearing devices for back-up rolls in this type of rolling mill which are known from the prior art are as shown in FIG. 3. This bearing device which is disposed between a roll shaft 31 on a static side of a back-up roll and an outer casing 32 on a rolling side of the back-up roll has a pair of inner rings 34, 34 fit and fixed outside the roll shaft 31, said inner rings 34, 34 being separated by a spacer ring 33 on the outside of said roll shaft 31, and having fit on both ends circular side plates 35 and snap rings 36; on the inside of the aforementioned outer casing 32 is fit and secured a pair of outer rings 37, 37 facing the aforementioned inner rings 34, 34; on both ends of these outer rings are fit circular covers 38 which are fixed to the outer casing 32 with bolts 39, and between aforementioned inner rings 34, 34 and outer rings 37, 37 are cylindrical rollers 41, 41 connected by retainers 40. Furthermore, flanges 42 contacting the ends of cylindrical rollers 41 are formed at the outer ends of inner rings 34, 34 and at the outer ends, inner ends, and middle of outer rings 37, and the axial thrust load acting on cylindrical rollers 41 is received by these flanges 42.
It is known that because back-up rolls such as this are installed above and below a pair of work rolls, and that bending of the work rolls is corrected by sandwiching the work rolls between upper and lower outer casings 32 which rotate and apply a heavy load to the roll shafts of the top and bottom work rolls in the direction in which both shafts drift, a large radial load of an average 30 tons acts in the radial direction and a very large thrust load of an average 1.5 ton acts in the axial direction of the bearing device. However, as will be evident from FIG. 3, because the aforementioned conventional bearing device is constructed in such a manner that this very large thrust load is received only by flanges 42 which are formed extending slightly at the ends of the inner and outer rings 34 and 37, respectively, when the excessive thrust load frequently produced during rolling is received, flanges 42 may fail, fragments of the flanges 42 may be caught in cylindrical rollers 41, and the back-up roll itself may become inoperable.